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Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Lighthouse with a sweeping beam in one self-contained HTML file

AClaude Sonnet 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-20 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first try
Estimated cost
$0.05
Wall time
20s
Human step-ins
0
Outcome
Pass

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Summary

Exact prompt

# Lighthouse with a sweeping beam in one self-contained HTML file Make a night-time lighthouse with a sweeping beam over the sea. Style, colours and technique (CSS, SVG, canvas) are up to you. **Looks are not scored**; only the objective checks below are. Write one file, `lighthouse.html`, in the working directory. ## Checks (all must pass; partial credit = fraction passed) 1. `file_exists_under_size_limit`: `lighthouse.html` exists and is at most 100,000 bytes (100 KB). 2. `no_external_requests`: fully self-contained. No `http://`, `https://` or `//` URLs in `src`, `href`, `srcset`, `poster`, `action`, `data` or `url()`, no asset URLs anywhere, no `@import`, `fetch(`, `XMLHttpRequest`, `WebSocket`, `EventSource`, `sendBeacon`, JS `import`, `<script src>` or `<link href>` (inline everything; `data:` URIs are fine). When a browser is used, any non-file request the page attempts also fails this check. 3. `animation_present`: CSS `@keyframes` plus an `animation`/`animation-name` property, or `requestAnimationFrame(` / `setInterval(`. 4. `loops_forever`: an `infinite` CSS animation (`animation-iteration-count: infinite` or `infinite` in the `animation` shorthand), or rAF/`setInterval` with no `cancelAnimationFrame`/`clearInterval` anywhere; when a browser is used, the page must also still change between ~6 s and ~7 s after load. 5. `page_animates`: when a headless Chrome/Chromium is available, the page is opened once with the network blocked at 800x600, and screenshots at ~1.5 s and ~2.5 s after load must differ. Without a browser (or if it fails to start) this and the browser part of check 4 fall back to the static checks 3-4; the scorer reports `check_mode` (`headless-browser` or `static-fallback`). 6. `required_id_and_title`: an element with `id="lighthouse"` and a `<title>` containing "Lighthouse" (case-insensitive). No other files, no build step, no network. Run time limit for scoring: 120 s.

Draw a lighthouse with a sweeping light beam as a single offline, looping HTML animation. Scoring is purely objective: under 100 KB, no external requests with the network blocked, an animation that loops forever and changes between headless Chrome screenshots, and the required element id and title. A public poll judges which version looks best. Original benchmark task written for usecaserank.com (not based on a specific public post). Headless, offline run on a reproducible fixture. Each run's notes say how its cost was measured (estimates are marked).

Success criteria: 1. file_exists_under_size_limit 2. no_external_requests 3. animation_present 4. loops_forever 5. page_animates 6. required_id_and_title

Setup notes: Use Case Scout batch 11 case l06-lighthouse-beam (offline, open-ended creative brief). Prepared with batch11/prepare.sh; hidden checker kept outside the agent's work dir. Prompt = TASK.md verbatim. Scored with the case's scorer (`python score.py WORKDIR KEYDIR`, headless Chrome over a CDP pipe, network blocked). Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. Output rendered offline (google-chrome headless, network blocked): PNG 1280x800 at ~3 s after load; MP4 1280x720 H.264 ~6 s. Claude Code's own reported cost for claude-sonnet-5.5: $0.053025. Score: 6/6. Cost is an ESTIMATE: measured tokens x pricing.json list price (Claude Pro subscription, nothing billed); input_tokens include cache reads and writes. Single run.

Estimated cost List-price estimate; not actually billed.

Output

Metrics

Estimated cost
$0.05
Wall time
20s
Human step-ins
0
Turns
2
Model usage
ModelInput tokOutput tokCost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking on38,9011,891$0.05

Reproduce this run

  1. Use the use case prompt on the use case page.
  2. Same setup: Claude Sonnet 5.5 (anthropic/claude-sonnet-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
  3. It counts as a success only if it meets every success criterion: 1. file_exists_under_size_limit 2. no_external_requests 3. animation_present 4. loops_forever 5. page_animates 6. required_id_and_title
  4. Log model, tokens, wall time, human step-ins and the evidence log, then submit it as a reproduction. A different model? Submit a head-to-head rerun.

How runs are scored: Methodology.

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Automated checks

Trust 80% comes from these checks (how Trust % works).

Evidence log
[
 {
  "duration_api_ms": 18871,
  "stop_reason": "end_turn",
  "session_id": "[REDACTED]",
  "total_cost_usd": 0.05302489999999999,
  "usage": {
   "input_tokens": 4,
   "cache_creation_input_tokens": 7748,
   "cache_read_input_tokens": 31149,
   "output_tokens": 1891,
   "output_tokens_details": {
    "thinking_tokens": 57
   },
   "server_tool_use": {
    "web_search_requests": 0,
    "web_fetch_requests": 0
   },
   "service_tier": "standard",
   "cache_creation": {
    "ephemeral_1h_input_tokens": 7748,
    "ephemeral_5m_input_tokens": 0
   },
   "inference_geo": "global",
   "iterations": [
    {
     "input_tokens": 2,
     "output_tokens": 302,
     "cache_read_input_tokens": 18610,
     "cache_creation_input_tokens": 1677,
     "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 1677
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
   "claude-sonnet-5-5": {
    "inputTokens": 4,
    "outputTokens": 1891,
    "cacheReadInputTokens": 31149,
    "cacheCreationInputTokens": 7748,
    "webSearchRequests": 0,
    "costUSD": 0.05302489999999999,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 57,
    "canonicalModel": "claude-sonnet-5-5",
    "provider": "firstParty",
    "costBasis": "list"
   }
  },
  "permission_denials": [],
  "terminal_reason": "completed",
  "fast_mode_state": "off",
  "fast_mode_disabled_reason": "sdk_opt_in_required",
  "subagent_stats": {
   "spawned": 0,
   "requested": {
    "background": 0,
    "foreground": 0,
    "unset": 0
   },
   "started_in_background": 0,
   "max_depth": 0,
   "spawned_by_subagents": 0,
   "completed": 0,
   "failed": 0,
   "killed": {
    "parent": 0,
    "user": 0,
    "system": 0
   },
   "refused": {
    "depth_limit": 0,
    "concurrency_limit": 0,
    "budget": 0
   },
   "by_type": {}
  },
  "safety_stops": 0,
  "is_error": false,
  "num_turns": 2,
  "subtype": "success",
  "api_error_status": null,
  "result": "I wrote `lighthouse.html` in the working directory, but I haven't opened it in a browser or run any of the checks.\n\n- **Scene:** A night sky with twinkling stars, a red-and-white lighthouse on a rock, and drifting waves on a dark sea.\n- **Beam:** A yellow beam rotates around the lamp once every 6 seconds in an infinite CSS animation.\n- **Required parts:** The lighthouse group has `id=\"lighthouse\"`, and the title is \"Lighthouse at Night\".\n- **Self-contained:** It has no external URLs or scripts. It's a small single file, well under 100 KB.\n\nThe beam points one way only, so it sweeps past the viewer once per turn rather than lighting both sides.",
  "ttft_ms": 14048,
  "type": "result",
  "duration_ms": 19158,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 4529,
  "time_to_request_ms": 250,
  "first_content_frame_ms": 4530,
  "queued_turn_count": 0,
  "result_index": 0
 }
]

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